/*
* Generic OPP Interface
*
*
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/cpufreq.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/opp.h>
/*
* Internal data structure organization with the OPP layer library is as
* follows:
* dev_opp_list (root)
* |- device 1 (represents voltage domain 1)
* | |- opp 1 (availability, freq, voltage)
* | |- opp 2 ..
* ... ...
* | `- opp n ..
* |- device 2 (represents the next voltage domain)
* ...
* `- device m (represents mth voltage domain)
* device 1, 2.. are represented by dev_opp structure while each opp
* is represented by the opp structure.
*/
/**
* struct opp - Generic OPP description structure
* @node: opp list node. The nodes are maintained throughout the lifetime
* of boot. It is expected only an optimal set of OPPs are
* added to the library by the SoC framework.
* RCU usage: opp list is traversed with RCU locks. node
* modification is possible realtime, hence the modifications
* are protected by the dev_opp_list_lock for integrity.
* IMPORTANT: the opp nodes should be maintained in increasing
* order.
* @available: true/false - marks if this OPP as available or not
* @rate: Frequency in hertz
* @u_volt: Nominal voltage in microvolts corresponding to this OPP
* @dev_opp: points back to the device_opp struct this opp belongs to
*
* This structure stores the OPP information for a given device.
*/
struct opp {
struct list_head node;
bool available;
unsigned long rate;
unsigned long u_volt;
struct device_opp *dev_opp;
};
/**
* struct device_opp - Device opp structure
* @node: list node - contains the devices with OPPs that
* have been registered. Nodes once added are not modified in this
* list.
* RCU usage: nodes are not modified in the list of device_opp,
* however addition is possible and is secured by dev_opp_list_lock
* @dev: device pointer
* @opp_list: list of opps
*
* This is an internal data structure maintaining the link to opps attached to
* a device. This structure is not meant to be shared to users as it is
* meant for book keeping and private to OPP library
*/
struct device_opp {
struct list_head node;
struct device *dev;
struct list_head opp_list;
};
/*
* The root of the list of all devices. All device_opp structures branch off
* from here, with each device_opp containing the list of opp it supports in
* various states of availability.
*/
static LIST_HEAD(dev_opp_list);
/* Lock to allow exclusive modification to the device and opp lists */
static DEFINE_MUTEX(dev_opp_list_lock);
/**
* find_device_opp() - find device_opp struct using device pointer
* @dev: device pointer used to lookup device OPPs
*
* Search list of device OPPs for one containing matching device. Does a RCU
* reader operation to grab the pointer needed.
*
* Returns pointer to 'struct device_opp' if found, otherwise -ENODEV or
* -EINVAL based on type of error.
*
* Locking: This function must be called under rcu_read_lock(). device_opp
* is a RCU protected pointer. This means that device_opp is valid as long
* as we are under RCU lock.
*/
static struct device_opp *find_device_opp(struct device *dev)
{
struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);
if (unlikely(IS_ERR_OR_NULL(dev))) {
pr_err("%s: Invalid parameters\n", __func__);
return ERR_PTR(-EINVAL);
}
list_for_each_entry_rcu(tmp_dev_opp, &dev_opp_list, node) {
if (tmp_dev_opp->dev == dev) {
dev_opp = tmp_dev_opp;
break;
}
}
return dev_opp;
}
/**
* opp_get_voltage() - Gets the voltage corresponding to an available opp
* @opp: opp for which voltage has to be returned for
*
* Return voltage in micro volt corresponding to the opp, else
* return 0
*
* Locking: This function must be called under rcu_read_lock(). opp is a rcu
* protected pointer. This means that opp which could have been fetched by
* opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
* under RCU lock. The pointer returned by the opp_find_freq family must be
* used in the same section as the usage of this function with the pointer
* prior to unlocking with rcu_read_unlock() to maintain the integrity of the
* pointer.
*/
unsigned long opp_get_voltage(struct opp *opp)
{
struct opp *tmp_opp;
unsigned long v = 0;
tmp_opp = rcu_dereference(opp);
if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
pr_err("%s: Invalid parameters\n", __func__);
else
v = tmp_opp->u_volt;
return v;
}
/**
* opp_get_freq() - Gets the frequency corresponding to an available opp
* @opp: opp for which frequency has to be returned for
*
* Return frequency in hertz corresponding to the opp, else
* return 0
*
* Locking: This function must be called under rcu_read_lock(). opp is a rcu
* protected pointer. This means that opp which could have been fetched by
* opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
* under RCU lock. The pointer returned by the opp_find_freq family must be
* used in the same section as the usage of this function with the pointer
* prior to unlocking with rcu_read_unlock() to maintain the integrity of the
* pointer.
*/
unsigned long opp_get_freq(struct opp *opp)
{
struct opp *tmp_opp;
unsigned long f = 0;
tmp_opp = rcu_dereference(opp);
if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
pr_err("%s: Invalid parameters\n", __func__);
else
f = tmp_opp->rate;
return f;
}
/**
* opp_get_opp_count() - Get number of opps available in the opp list
* @dev: device for which we do this operation
*
* This function returns the number of available opps if there are any,
* else returns 0 if none or the corresponding error value.
*
* Locking: This function must be called under rcu_read_lock(). This function
* internally references two RCU protected structures: device_opp and opp which
* are safe as long as we are under a common RCU locked section.
*/
int opp_get_opp_count(struct device *dev)
{
struct device_opp *dev_opp;
struct opp *temp_opp;
int count = 0;
dev_opp = find_device_opp(dev);
if (IS_ERR(dev_opp)) {
int r = PTR_ERR(dev_opp);
dev_err(dev, "%s: device OPP not found (%d)\n", __func__, r);
return r;
}
list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
if (temp_opp->available)
count++;
}
return count;
}
/**
* opp_find_freq_exact() - search for an exact frequency
* @dev: device for which we do this operation
* @freq: frequency to search for
* @available: true/false - match for available opp
*
* Searches for exact match in the opp list and returns pointer to the matching
* opp if found, else returns ERR_PTR in case of error and should be handled
* using IS_ERR.
*
* Note: available is a modifier for the search. if available=true, then the
* match is for exact matching frequency and is available in the stored OPP
* table. if false, the match is for exact frequency which is not available.
*
* This provides a mechanism to enable an opp which is not available currently
* or the opposite as well.
*
* Locking: This function must be called under rcu_read_lock(). opp is a rcu
* protected pointer. The reason for the same is that the opp pointer which is
* returned will remain valid for use with opp_get_{voltage, freq} only while
* under the locked area. The pointer returned must be used prior to unlocking
* with rcu_read_unlock() to maintain the integrity of the pointer.
*/
struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq,
bool available)
{
struct device_opp *dev_opp;
struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
dev_opp = find_device_opp(dev);
if (IS_ERR(dev_opp)) {
int r = P
